Although efforts are being made to solve some of today's network transparency constraints, the solutions offered are still constrained by the rigid rules of today's North American Numbering Plan (NANP) and the architecture which supports it. That is, each telephone subscriber has a number in the NXX-NXX-XXXX format, where N represents a digit from 2-9 and X represents a digit from 0-9. The first group of three digits indicates the area code or NPA of the subscriber, the second group of three digits indicates a switching exchange or service switching point to which the subscriber is connected, and the last four digits indicate the address of the subscriber within the service switching point. Digits 0 and 1 are of course not available as the first digit (N) to allow operator and long distance services.
With the large increase in telephone devices of one sort or another, an equivalent increase in the demand of telephone numbers has been created. For example, 15 years ago, most telephone numbers were used for fixed Plain Ordinary Telephone Service (POTS) devices. Today, more and more users make use of several devices, such as cellular telephones, pagers, fax machines, modems, etc. This demand has placed a large impact on the pool of numbers available for customers. In some instances, metropolitan areas that used to be served by one area code, now require several. The problem is, of course, compounded by the need to assign new telephone numbers to subscribers who move from one region to another. In addition, numbers must, in future, be portable between networks, namely between the Incumbent Local Exchange Carriers (ILEC) and Competitive Local Exchange Carriers (CLEC).
To help reduce this need for new numbers, network facilitators have been unsuccessfully researching options for delivering a service in which telephone numbers are not tied to equipment locations.
New telephone networks with Advanced Intelligent Network (AIN) concepts have been proposed to support faster development of new services through a network architecture in which network functions and interfaces are standardized providing greater independence between service software and technology.
One service application which makes use of AIN technology for separating dialling from physical routing is Local Number Portability (LNP). The applications are being examined by the Information Industry Liaison Committee (IITC) for extension of LNP concepts. Many options have been discussed and are being investigated. The options to route based on network number ownership fall short, in the sense that they impose various limitations, and are at this time unworkable.
The current direction for network evolution is to remove intelligence from the telephone exchange using database query procedures to increase network flexibility. Where initial decisions can be made for launching a query to a database, increased flexibility can be easily obtained, usually with reduced costs. However, the costs increase dramatically when all calls from a specific exchange require this procedure. Costs associated with the database query implementation include:
AIN and/or vendor license charges (usually on a per dip basis), PA1 Increase in exchange CPU requirements (factor of 2-5 per call), PA1 Augment of the signalling network, PA1 Database infrastructure required to support queries, and PA1 Database updates to keep all systems current. PA1 a) forwarding an Initial Address Message (IAM) from an originating office to a terminating office, said IAM containing the calling and called party's numbers to enable said call to reach said terminating office; PA1 b) receiving said IAM at said terminating office and determining whether said call is directed to a portable number; PA1 c) if said call is directed to a portable number, accessing a routing database to obtain a new routing option to enable said call to be routed to said called party; PA1 d) creating at said terminating office a message containing an indication that the called party number is a portable number along with said new routing option; PA1 e) sending said message from said terminating office to said originating office; PA1 f) receiving said message, at said originating office; and PA1 g) creating a new IAM to enable the call to reach the called party. PA1 a) a first switching office for creating an Initial Address Message (IAM), said IAM containing the calling and called party's numbers to enable said call to reach said called party; PA1 b) a second switching office connected to said first switching office via a signalling path established for routing said call and for receiving said IAM; PA1 c) first database means, at said second switching office for determining whether said call is directed to a portable number; PA1 d) means at said second switching office for creating a message containing an indication that the called party number is a portable number along with said new routing information; PA1 e) means for receiving, at said first switching office, said message returned from said second switching office, such that when said new routing information is received at said first switching office, a new IAM is forwarded via the network to an alternate terminating office associated with said new routing information.
Number portability requires the treatment of all calls to a specific number irrespective of the point of origin, making the terminating switch the most logical location to control the call. Initially, this concept presents an inexpensive option for allowing portability, but as the numbers increase, many additional circuits will be required. At this point release link trunks can be employed to reduce the connections, but this requires a common protocol and significant interconnection development.
Most solutions carry significant development requirements and it is therefore important to choose the option which can support the requirements over the long term.
Two options are the most widely recognized and popular at present. The first is to use AIN technology to use a query and response procedure for each call to query a database to establish number ownership. The second option is that of Terminating Switch Routing. This proposal consists of the routing of calls using the existing NANP to the expected terminating switch location where, when numbers are owned by another network, calls are then route advanced to that network. In some cases, release link trunks are envisioned to reduce the number of circuits required.
Some problems still exist in implementing these proposed methods, including flash cuts, calls being routed several times between networks and inefficient routing schemes. In addition, the solutions proposed above, are meant to make use of AIN technology. Although AIN is considered a subset of Intelligent Networks (IN), number portability should not be limited to AIN networks only.
A need therefore exists for providing a mechanism to take advantage of these various methods while providing the flexibility to eliminate single option constraints.
It is therefore an object of the present invention to provide number portability which overcomes the aforementioned problems.
Another object of the present invention is to provide a method of routing calls between networks with ported numbers while making use of existing facilities, minimizing call routing complexities and costs.
Another object of the present invention is to provide a method of routing calls to provide number portability, which makes use of the flexibility provided by ISUP signalling.
Another object of the present invention is to provide number portability by modifying ISUP signalling messages to enable the modified message to provide a new routing option for calls which are directed to directory numbers determined to be portable.
Yet another object of the present invention is to provide a method of providing number portability by modifying the ISUP message transmitted from the terminating switch, to provide an indication to the originating switch that the directory number is determined to be portable.
Yet another object of the present invention is to provide a method of providing number portability by modifying an ISUP message parameter capable of carrying routing information such that a new routing option can be forwarded from the terminating switch back to the originating switch for completing the call.
Yet another object of the present invention is to provide number portability for calls originating from network switching nodes unable to support number portability.